Series lamp



July 23,1940. I A. 5mm. 2,209,005

SERIES LAMP Filed June 27, 1959 Inventor: Alfred Sittel,

His Attorney.

Patented July 23, 1940 UNITED STATES PATENT OFFICE scams LAMP Alfred Sittel, Schoneiche, near Berlin, Germany,

assignor to General Electric Company, a corporation oi. New York Application June 27, 1939, Serial no. 281,494

In Germany July 4, 1938 3 Claims.

-sult.of the filament failure.

the connection cable by any are which may be formed within the lamp and which may extend further or become unnecessarily long. The melting together of the current supply wires also assures the continued uninterrupted passage of the 5 current through the other lamps of the group so that the latter cannot be extinguished as a re- When, in the described lamp according to the invention, a failure that when the filament of a lamp fails, the cutof the filament occurs while in the cold state, then 10 out is rendered conductive and the other lamps *th'e cut-out of the damagedllamp will immediof the group will continue'to burn by an autoately respond when the lamp group is switched matic short circuiting of the lamp; or if the on. In such case, no arc will be formed at the failure occurs while the filament is unlighted, broken filament.

the other lamps of the group maythereby be At the time during which carbon-rod filaments is placed in operation merely by closing the circuit. were used in electric incandescent lamps, it was The cut-outs used for such incandescent lamps occasionally suggested to bring the current'supoperated in a series circuit have been designed ply wires which supported the carbon-rod filain many difierent ways. Generally they consist ments, close together at a point below the filaof oxidized aluminum wires or aluminum strips ment, for series-connection purposes, so that 20 which are placed around the two current supply when the filament burned through, the are that wires of the lamps within the stem tube of the might be formed would melt together the parts lamp. These cut-outs respond with great relia of the current supply wires that were brought bility when the filament of the lamp breaks when close to each other, ior'the purpose of establishit is not burning and therefore while it is cold, ing a current path. However, this suggestion 25 but they do not respond as reliably when the. did not, by itself, gain practical importance filament fails while burning. In the latter case either for the lamps with carbon-rod filaments it happens, particularly when the series-conused at that time or for lamps with filaments nected incandescent lamp operates in circuits made of tungsten wire that were used subsewith voltages in excess of 220 volts, such as in quently. I'he reason for this was that on the circuits for electric railways, that between the broken ends of the filament an arc is formed which takes up the partial voltage of the point of the break. As a result, the current will con tinue to flow over the filament, and the full network voltage which is required for breaking down the cut-out is therefore never impressed thereupon. If an arc should occur, it may readily extend itself to the current supply wires while 40 r the current increases, and then frequently leads not only to a destruction of the lamp bulb but also of the base and of the fitting. In extreme cases, even the connection cable may catch fire.

This disadvantage, which occurs in electric in candescent lamps connected in series, can be avoided when, according to the inventio the current supply wires are not only brldg dby a cut-out, but when in addition they are brought so' close to each other at a point between the, filament and the stem tube that the parts oi. the current supply wires located at the point of proximity are melted together when an arc occurs. Since the arc is extinguished when the current supply wires melttogether, no damage can be caused to the base, to the fitting and to one hand, such a measure fails when the filament breaks while cold and consequently does not prevent the extinguishment oi the lamps of the entire group when the circuit is switched on again, and in the second place because when 35 the filament fails during operation, an are which would cause the melting together of the current supply wires is not always formed, and is formed but rarely in the case or" series-connection lamps burning in circuits of to 220 volts, as is the case for instance with illuminating lamps and candle-type lamps.

One object of my invention is to provide means for series=operating electric incandescent lamps which will prevent the extinguishrnent of all the lamps in the series upon the failure of any one lamp therein.

Another object oi my invention is to provide automatic cut-out means for series-operating electric incandescent lamps which will positively 50 operate to short-circuit the lamp filament and interconnect the lamp leading-in wires upon failure of the said filament, regardless of whether such failure occur during lamp operation or otherwise. V

' mined distance from each other.

Further objects and advantagesof my invention will appear from the following description and from the accompanying drawing which is an elevation, partly in section, of an electric incandescent lamp comprising my invention for series operation, and in particular, for use on railroad trains with trolley-wire voltages in ex-' cess of 440 v tes.

Referr' to the drawing, the lamp there shown consists in the customary manner of a glass bulb I, a stem tube 2 extending inwardly of the bulb, two current supply or leading-in wires 4, hermetically sealed in the stem press 3 of the stem tube, a sealed evacuation tube 6, and a filament 'l which may consist of a single or double coil of tungsten wire and which is welded, or fastened by pinching, to the ends of the two current supply wires 6, 5. One of the said wires i s soldered to the sleeve 8, and the other to the bottom contact 9 of a customary screw base.

The outer leads 815', i. e., the parts of the two 7 current supply wires whichextend between the stem press 3 and the lamp base, are bridged by a clamp of oxidized aluminum strip") which constitutes the breakdown fuse or cut-out of the lamp. This cut-out always responds when the filament 1 fails while cold, and under certain circumstances will also respond when the filament fails in the heated condition. The latter response occurs when an arc is not immediately formed upon failure of the filament during operation, so that the lamp is consequently extinguished. Between the coiled filament I and the stem press 3 of the stem tube 2, the two inner leads 6, 5 of the current supply wires are provided with two acute-angle impressions ll, l2

which are directed toward each other and which approach each other to a distance of 1 mm. or less. If, when the filament fails during lamp operation, an arc is formed between the 'broken ends of the filament, and when this arc, as customarily occurs, passes down along the current supply wires 4, 5, towards the stem press 3, then the parts of the impressions ll, 12 which are located in close proximity to eami other will be meltedtogether by the arc, with resultant extinguishment of the arc. In order to prevent the inner current supply wires 4, 5 from springing apart when the filament 1 fails in the heated condition and when an arc is formed, and in order to insure a melting together of the current supply wires with great reliability, the said inner leadsare bridged, in an insulated manner, by means of a spacer member comprising a glass bead l3 which is held by wires I4, l5 welded to the inner current supply wires. The said spacer member maintains the spaced relation of the inner leads d, 5 at all times.

The shape of the filament, of the lamp bulb and of the base may be any desired one. The

cut-out it may also be of any other suitable c onstruction, and can in certain cases, as known, be located within the bulb instead of externally thereof.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric incandescent lamp comprising a sealed envelope, a filament within said envelope,

a base secured to said envelope, and a pair of leading-in wires connecting said filament to the terminals of said base, said leading-in wires including inner leads within said envelope having bent portions extending into sufiiciently close proximity to each other so that an arc formed upon failure of said filament and passing along said leads will fuse them together at their said bent portions, and 'a cut-out member bridging said leading-in wires at a point intermediate the base connections and the closely disposed portions of said leading-in wires, said cut-out member being spaced a considerable distance from the said closely disposed portions of said. leading-in wires and being normally non-conductive but becoming automatically conductive upon application of an abnormal voltage to the lamp.

2. An electric incandescent lamp comprising a sealed envelope, a filament within said envelope,

leading-in wires connecting said filament to the terminals of said base, said leading-in wires including inner leads within said envelope having bent portions extending into close proximity to each other, and a cut-out member bridging said leading-in wires externally of said envelope.

3. An electric incandescent lamp comprising a sealed envelope, a filament within said envelope, a base secured to said envelope, and a pair of leading-in wires connecting said filament to the a base secured to said envelope, and a pair of terminals of said base, said leading-in wires in-' cluding inner leads within said envelope having bent portions extending into close proximity to each other, a cut-out member bridging said leading-in wires externally ofsaid envelope, and a spacer member bridging said. leading-in wires internally of said envelope and maintaining the said bent'portions of said leading-in wires in definite close proximity to'each other.

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